A rotary crop baler of the general type to which this invention relates is disclosed in U.S. Pat. No. 3,914,926 to Braunberger et al. U.S. Pat. Nos. 4,257,219, to Burrough et al, and 4,244,167, to Seefeld et al, disclose improvements in such a machine. All of those patents have a common assignee with this application.
In general, a rotary crop baler comprises a frame mounted on wheels to be towed behind a tractor or the like and having opposite upright side walls. A pickup means on a front portion of the frame picks up cut crop material as the baler moves forward, discharging the material rearwardly towards a gap between upper and lower feed rollers that rotate on parallel horizontal axes and extend from one to the other of the side walls on the frame. The feed rollers, which are driven for rotation in opposite directions, cooperate to deliver the crop rearwardly into a bale forming zone, where the crop is confined between a rearwardly moving supporting surface and a forwardly moving surface, to be rolled into a cylindrical bale. The forwardly moving surface is defined by endless compacting belt means trained around belt rollers that have their axes parallel to those of the feed rollers, and particularly by an expandable stretch of the compacting belt means that extends between a pair of lowermost belt rollers. One of those lowermost belt rollers is located over the feed rollers, the other is spaced farther to the rear. Some of the other belt rollers around which the compacting belt means is trained are movable in a shuttle arrangement that maintains the expandable stretch under yielding lengthwise tension so that it can be displaced upwardly between the two lowermost belt rollers. As the bale forms and grows in diameter, it forces the expandable stretch upward and is at the same time contained by that stretch, which embraces the bale while imposing a radially compressive force upon it.
In the rotary crop balers of the above mentioned patents, the lower one of the two feed rollers did not directly engage the incoming crop but was, instead, a front one of a set of conveyor rollers arouhd which was trained a lower belt that had an upper, rearwardly moving platform stretch. The upper feed roller thus cooperated with the front portion of the platform stretch to feed crop rearwardly into the bale forming zone, the crop being carried rearwardly on the platform stretch, which was located beneath the expandable stretch of the compacting belt means. FIGS. 2 and 5 of the drawings in the above mentioned Seefeld et al patent depict the manner in which the lower belt cooperates with the compacting belt means in developing a bale core and forming a bale.
It was obviously desirable to eliminate the lower belt if a satisfactory substitute for it could be devised, in order to avoid the inevitable problems involved in maintaining that belt tensioned around its supporting and driving rollers and in repairing or replacing it from time to time. The lower belt also had a functional disadvantage with respect to the baling of certain types of crop materials, particularly those that were cut short or were very dry and slippery. With such materials there was often difficulty in forming a satisfactory core during the initial stage of a bale forming operation. Before being displaced upward by a growing bale, the expandable stretch of the compacting belt means extended substantially horizontally, and it defined a substantially triangular bale starting chamber with the platform stretch of the lower belt, which slanted rearwardly and upwardly towards the expandable stretch. It was evident that the triangular configuration of this bale starting chamber accounted for the occasional inability to form a satisfactory core, because formation of a compact cylindrical bale core is best encouraged with a bale starting chamber that is as nearly as possible cylindrical.
Rotary balers have heretofore been devised that do not have a lower belt, and such balers have operated satisfactorily with most crop materials, but they have had bale starting chambers that departed markedly from a cylindrical configuration, and therefore the inability to form a compact bale core with dry and short cut crop materials has been common to prior art rotary balers generally.